Alternative Powertrains and “Hybrids”
Alternative Powertrain is used as a synonym for all propulsion systems in a vehicle which are not based only by a gasoline or diesel fueled Internal Combustion Engine (ICE).
Today the electric vehicles (EV), powered by batteries or hydrogen fuel FCV (Fuel Cell Vehicle), are pure alternative powertrain vehicles. "Hybrid Vehicles", a steadily growing portion of the passenger cars, in the mainstream named HEV (Hybrid Electric Vehicle) or PHEV (Plug-in Hybrid Electric Vehicle), are a combination of two powertrains.
They consist of a regular ICE as known and they have an additional electric motor powered by a battery package. Both powertrains can act as single drives or simultaneous in the case of high power demand. This depends very much on the actual driving condition. In the HEV version, the vehicle is able to run a few kilometers only on electric power, mainly the ICE takes the part of the driving.
Or the electric powertrain part is only activated on high power demand, e.g. strong acceleration. The PHEV segment is growing, especially in SUV and full size vehicles due to the strong demand of reducing CO2 emissions. PHEV’s can drive significant more range in electric mode and can be recharged by a cable and a power outlet from the power grid (e.g. charging station or in a garage).
Both HEV’s and PHEV’s have a regular fuel system for liquid fuel as it is state of the art today, meaning a plastic fuel system. A special case is the fuel tank for the PHEV’s. As it is legally requested by emission requirements, the fuel system of a PHEV has to be sealed during electric drive mode or parking.
Hence, due to the basic physics the fuel raises its vapor pressure at elevated temperatures and creates a slight overpressure in the tank, also by cooling down this can create a vacuum in the tank as well. Innovative internal stiffening elements have been developed to cope with pressure variations of these tanks. Those systems continue to offer the traditional benefits of plastics.